1. Field of the Invention
The present invention relates to a method of making liquid crystal display elements and more particularly, to a method of making liquid crystal elements capable of providing a uniform gap therein by selecting glass spacers of a uniform size according to the use of a ceramic filter and mixing them in a liquid crystal orientation solution along with a dilution solvent and then printing the mixture on a glass substrate with a certain pattern.
2. Description of the Prior Art
Several types of methods of making liquid crystal display elements are well known in the art. Referring to FIGS. 1 and 2, there is illustrated a conventional method of making liquid crystal elements. In the method shown in FIGS. 1 and 2, a mixture containing a liquid crystal orientation solution is coated by a printing on a glass substrate 9 with a certain pattern indicative of characters and figures of a liquid crystal display element to be produced. That is, the mixture is first prepared by uniformly mixing the liquid crystal orientation solution with a solvent at the ratio of 1:2, and then adding bar type glass spacers (glass fibers) in the mixture. Thereafter, as the mixture containing glass spacers is coated on the glass substrate 9 with a certain pattern, a liquid crystal display element is produced.
The liquid crystal orientation solution used in making liquid crystal display elements is a polyimide solution which is a high viscous solution exhibiting a yellow brown color and having a solid content of about 3% to 15% by weight. To have a viscosity of about 200 cps to 300 cps that is proper in printing, the solution is diluted with butyl cellosolve or N.M.P. (normal methyl formamide). Thereafter, glass spacers are added in the diluted solution and mixed well therein by a magnetic stirrer to be uniformly dispersed therein. The produced mixture containing the liquid crystal orientation solution and glass spacers is then coated, by a printing, on the ITO (indium tin oxide) glass substrate 9 with a certain pattern as shown in FIG. 2.
The bar type glass spacers which are of various modules having different sizes are available commercially. The size is based on the height of diameter of glass spacers and is generally 7.0 .mu.m, 8.0 .mu.m, or 9.0 .mu.m.
Such glass spacers are contained in the liquid crystal orientation solution in a predetermined amount for maintaining the gap in each cell of liquid crystal display element. Normally, they are measured in length and in height by an electromicroscope and then added in the liquid crystal orientation solution of about 500 g, in a predetermined amount of, for example, about 50 g. However, it is difficult to measure the size of glass spacers one by one by using the electromicroscope. In particular, there is a limitation in making a large liquid crystal display element requiring an accurate gap.
Furthermore, the glass spacers which are commercially available as products having the size of 9 .mu.m may contain glass spacers having the size of 10 .mu.m up to 10%, as shown in FIG. 3. Such glass spacers of irregular size cause the irregularity of cell gaps in the produced liquid crystal display elements. In the conventional method, since the glass spacers are directly added in the mixture containing the liquid crystal orientation solution and the solvent, the often lump together. This phenomenon of glass spacers results in the irregularity of appearing colors of liquid crystal display elements.